In related art, a lighting device is known, which includes a device main body which accommodate therein a mounting plate, a terminal block and a connector, wherein a light source block including an LED circuit board and a lens element which serves as an optical member, a lighting controller and a heat conducting sheet are mounted on the mounting plate (for example, refer to Patent Document 1).
In Patent Document 1, in a state in which a surface of the LED circuit board on which LEDs are mounted is oriented downward the LED circuit board is brought into contact with a lower surface portion of the mounting plate via the heat conducting sheet, and the lens element is disposed on the lower surface portion of the mounting plate so as to accommodate the LED circuit board in an accommodating portion of the lens element such that the LEDs correspond to respective recess portions of the lens element.
In Patent Document 1, the lens element is mounted on the mounting plate by inserting screws through cutouts formed in projecting pieces of the lens element via a spacer and a packing, and screwing the screws into a pair of screw holes formed in the mounting plate so as to correspond to the screws.